Numerous conventional methods exist for producing polyalphaolefin (PAO) compositions. However, these methods suffer from inefficiencies and there remains a need for more effective methods for making polyalphaolefins. Also there remains a need for polyalphaolefins (PAOs) having improved properties.
In a conventional polyalphaolefin process, product kinematic viscosities can be adjusted by either removing or adding higher or lower oligomers to provide a composition having the desired viscosity for a particular application. Viscosities in the range of 2 to 100 cSt, 2 to 10 cSt, and 4 cSt at 100° C. are useful.
A particularly large market exists for synthetic lubricant base stocks having kinematic viscosity of 4 cSt at 100° C. especially if this property is combined with low Noack volatility, low pour point, useful low temperature viscosity, and high viscosity index. The 4 cSt PAO made in the decene oligomerization provides a useful balance of properties. Unfortunately, the 4 cSt material (mainly decene trimer or C30) must be distilled from a complex oligomer mixture and is generally accompanied by a heavier co-product.
It is desirable to produce 4 cSt compositions having similar or better properties compared to decene-based oils from feed stocks other than decene—due to the limited decene supply. It is also desirable to produce the aforesaid 4 cSt composition selectively and without any co-products.
The present invention relates to a low viscosity polyalphaolefin (PAO) composition characterized by low Noack volatility, low pour point, inventive low temperature viscometrics, high viscosity index, and low sludge forming tendencies and more particularly concerns a PAO composition having a kinetic viscosity at 100° C. in the range of about 4 cSt. The invention also relates to an improved process for the selective production of the aforesaid composition without formation of any heavier co-products. Furthermore, the invention also relates to an improved process for the selective production of the aforesaid composition without formation of any heavier co-products comprising a very high (co)dimer content with minimal amounts of trimer and heavier oligomers using a BF3 catalyst along with a promoter system containing at least an ester and an embodiment consisting of an alcohol and an ester system in reaction involving at least one alpha olefin with at least one vinylidene olefin (a branched alpha olefin with alkyl substitution at the 2 carbon position).